ST72124J2 STMicroelectronics, ST72124J2 Datasheet - Page 32

• Manufacturer Part Number: ST72124J2
• Description: 8-BIT MCU WITH SINGLE VOLTAGE FLASH MEMORY,ADC, 16-BIT TIMERS, SPI, SCI INTERFACES
• Manufacturer: STMicroelectronics

Specifications of ST72124J2

• Clock Sources: crystal/ceramic resonator oscillators or RC oscillators, external clock, backup Clock Security System
• 4 Power Saving Modes: Halt, Active-Halt, Wait and Slow
• Two 16-bit Timers With: 2 input captures (only one on timer A), 2 output compares (only one on timer A), External clock input on timer A, PWM and Pulse generator modes

ST72334J/N, ST72314J/N, ST72124J
9.5 SUPPLY, RESET AND CLOCK REGISTER DESCRIPTION
Read /Write
Reset Value: 000x 000x (xxh)
Bit 7:5 = Reserved, always read as 0.
Bit 4 = LVDRF LVD reset flag
This bit indicates that the last RESET was gener-
ated by the LVD block. It is set by hardware (LVD
reset) and cleared by software (writing zero). See
WDGRF flag description for more details. When
the LVD is disabled by option byte, the LVDRF bit
value is undefined.
Bit 3 = Reserved, always read as 0.
Bit 2 = CSSIE Clock security syst
This bit enables the interrupt when a disturbance
is detected by the clock security system (CSSD bit
set). It is set and cleared by software.
0: Clock security system interrupt disabled
1: Clock security system interrupt enabled
Refer to
for more details on the CSS interrupt vector. When
the CSS is disabled by option byte, the CSSIE bit
has no effect.
Table 4. Clock, Reset and Supply Register Map and Reset Values
32/153
Address
7
0
(Hex.)
002Bh
0
Table 5, “Interrupt mapping,” on page 34
CRSR
Reset Value
Register
0
Label
LVD
RF
0
7
0
CSS
.
IE
interrupt enable
CSS
6
0
D
WDG
RF
0
5
0
Bit 1 = CSSD Clock security system detection
This bit indicates that the safe oscillator of the
clock security system block has been selected by
hardware due to a disturbance on the main clock
signal (f
This bit indicates that the last RESET was gener-
ated by the watchdog peripheral. It is set by hard-
ware (Watchdog RESET) and cleared by software
(writing zero) or an LVD RESET (to ensure a sta-
ble cleared state of the WDGRF flag when the
CPU starts).
Combined with the LVDRF flag information, the
flag description is given by the following table.
Application notes
The LVDRF flag is not cleared when another RE-
SET type occurs (external or watchdog), the
LVDRF flag remains set to keep trace of the origi-
nal failure.
In this case, a watchdog reset can be detected by
software while an external reset can not.
reading the CRSR register when the original oscil-
lator recovers.
0: Safe oscillator is not active
1: Safe oscillator has been activated
When the CSS is disabled by option byte, the
CSSD bit value is forced to 0.
Bit 0 = WDGRF Watchdog reset flag
External RESET pin
Watchdog
LVD
LVDRF
4
x
RESET Sources
OSC
). It is set by hardware and cleared by
3
0
CFIE
2
0
LVDRF
CSSD
1
0
0
0
1
WDGRF
WDGRF
0
X
x
0
1